This is a late 19th century button, rather imitative of a late 18th century button! The difference is in the style, construction, and materials but painting under glass genre goes back a ways. This lady in blue gown and bonnet is pretty and in very fine condition, painted on ivoroid celluloid, The rhinestones in the border of the brass mounting are still very bright and clean. It measures 1 & 1/8 inches (NBS medium) and in very fine to excellent condition.